Sulfur-carbon composite and lithium-sulfur battery including same

Abstract

A sulfur-carbon composite and a lithium-sulfur battery including the same, and in particular, to a sulfur-carbon composite including a porous carbon material; a polymer having electrolyte liquid loading capacity; and sulfur. The porous carbon material may be coated with the polymer having electrolyte liquid loading capacity and the coated porous carbon material then mixed with the sulfur. By introducing a coating layer including the polymer having electrolyte liquid loading capacity to a surface of the porous carbon material, it is possible to improve reactivity of the sulfur and an electrolyte liquid and thereby enhance performance and lifetime properties of the lithium-sulfur battery.

The invention claimed is: 
     
       1. A sulfur-carbon composite comprising:
 a porous carbon material; 
 a coating layer comprising a polymer having electrolyte liquid loading capacity; and 
 sulfur, 
 wherein the coating layer is present on at least an inner surface of the porous carbon material and the coating layer is present between the sulfur and the porous carbon material; and 
 wherein the polymer having electrolyte liquid loading capacity comprises polyurethane. 
 
     
     
       2. The sulfur-carbon composite of  claim 1 , wherein the coating layer-formed porous carbon material is mixed with the sulfur. 
     
     
       3. The sulfur-carbon composite of  claim 1 , wherein the polymer has an electrolyte liquid loading capacity of 50% or greater. 
     
     
       4. The sulfur-carbon composite of  claim 1 , wherein the polymer having electrolyte liquid loading capacity is present in an amount of from 0.1 parts by weight to 50 parts by weight, based on 100 parts by weight of the porous carbon material. 
     
     
       5. The sulfur-carbon composite of  claim 1 , wherein the porous carbon material comprises at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, carbon fibers, natural graphite, artificial graphite, expanded graphite and activated carbon. 
     
     
       6. The sulfur-carbon composite of  claim 1 , wherein the sulfur comprises at least one selected from the group consisting of inorganic sulfur of formula S 8 , Li 2 S n , wherein n≥1, disulfide compounds, organosulfur compounds and carbon-sulfur polymers of formula (C 2 S x ) n , wherein x=2.5 to 50, and n≥2. 
     
     
       7. The sulfur-carbon composite of  claim 1 , wherein a coating layer is present on both an inner surface of the porous carbon material and an outer surface of the porous carbon material. 
     
     
       8. The sulfur-carbon composite of  claim 1 , wherein the polyurethane is prepared through a reaction of a polyol and an isocyanate. 
     
     
       9. The sulfur-carbon composite of  claim 8 , wherein the polyol is selected from the group consisting of polyether-based polyols, polyester-based polyols, polytetramethylene ether glycol polyols, polyharnstoff dispersion (PHD) polyols, amine-modified polyols and mannich polyols. 
     
     
       10. The sulfur-carbon composite of  claim 8 , wherein the isocyanate is selected from the group consisting of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (H12MDI), polyethylene polyphenyl isocyanate, toluene diisocyanate (TDI), 2,2′-diphenylmethane diisocyanate (2,2′-MDI), 2,4′-diphenylmethane diisocyanate (2,4′-MDI), 4,4′-diphenylmethane diisocyanate (4,4′-MDI, monomeric MDI), polymeric diphenylmethane diisocyanate (polymeric MDI), ortho toluidine phenylmethane diisocyanate (TODI), naphthalene diisocyanate (NDI), xylene diisocyanate (XDI), lysine diisocyanate (LDI) and triphenylmethane triisocyanate (TPTI). 
     
     
       11. A positive electrode for a lithium-sulfur battery comprising the sulfur-carbon composite of  claim 1 . 
     
     
       12. A lithium-sulfur battery comprising the positive electrode of  claim 11 . 
     
     
       13. A method for preparing a sulfur-carbon composite according to  claim 1 , comprising the steps of:
 (a) coating a porous carbon material with a polymer having electrolyte liquid loading capacity and 
 (b) mixing the porous carbon material coated with the polymer having electrolyte liquid loading capacity prepared in (a) with sulfur, and molding the result. 
 
     
     
       14. The method for preparing a sulfur-carbon composite of  claim 13 , wherein the step (b) includes mixing the porous carbon material coated with the polymer having electrolyte liquid loading capacity with sulfur and heating and molding the result.